Effects of Ionic Liquid Alkyl Chain Length on Denaturation of Myoglobin by Anionic, Cationic, and Zwitterionic Detergents. 2019

Joshua Y Lee, and Katherine M Selfridge, and Eric M Kohn, and Timothy D Vaden, and Gregory A Caputo
Department of Chemistry and Biochemistry, Rowan University, Glassboro, NJ 08028, USA.

The unique electrochemical properties of ionic liquids (ILs) have motivated their use as solvents for organic synthesis and green energy applications. More recently, their potential in pharmaceutical chemistry has prompted investigation into their effects on biomolecules. There is evidence that some ILs can destabilize proteins via a detergent-like manner; however, the mechanism still remains unknown. Our hypothesis is that if ILs are denaturing proteins via a detergent-like mechanism, detergent-mediated protein unfolding should be enhanced in the presence of ILs. The properties of myoglobin was examined in the presence of a zwitterionic (N,N-dimethyl-N-dodecylglycine betaine (Empigen BB®, EBB)), cationic (tetradecyltrimethylammonium bromide (TTAB)), and anionic (sodium dodecyl sulfate (SDS)) detergent as well as ILs based on alkylated imidazolium chlorides. Protein structure was measured through a combination of absorbance, fluorescence, and circular dichroism (CD) spectroscopy: absorbance and CD were used to monitor heme complexation to myoglobin, and tryptophan fluorescence quenching was used as an indicator for heme dissociation. Notably, the detergents tested did not fully denature the protein but instead resulted in loss of the heme group. At low IL concentrations, heme dissociation remained a traditional, cooperative process; at high concentrations, ILs with increased detergent-like character exhibited a more complex pattern, which is most likely attributable to micellization of the ionic liquids or direct denaturation or heme dissociation induced by the ILs. These trends were consistent across all species of detergents. 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence was further used to characterize micelle formation in aqueous solutions containing detergent and ionic liquid. The dissociation thermodynamics show that EBB- and TTAB-induced dissociation of heme is not significantly impacted by room temperature ionic liquids (RTILs), whereas SDS-induced dissociation is more dramatically impacted by all RTILs examined. Together, these results indicate a complex interaction of detergents, likely based on headgroup charge, and the active component of RTILs to influence heme dissociation and potentially protein denaturation.

UI MeSH Term Description Entries
D008958 Models, Molecular Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures. Molecular Models,Model, Molecular,Molecular Model
D009211 Myoglobin A conjugated protein which is the oxygen-transporting pigment of muscle. It is made up of one globin polypeptide chain and one heme group.
D009930 Organic Chemicals A broad class of substances containing carbon and its derivatives. Many of these chemicals will frequently contain hydrogen with or without oxygen, nitrogen, sulfur, phosphorus, and other elements. They exist in either carbon chain or carbon ring form. Organic Chemical,Chemical, Organic,Chemicals, Organic
D012967 Sodium Dodecyl Sulfate An anionic surfactant, usually a mixture of sodium alkyl sulfates, mainly the lauryl; lowers surface tension of aqueous solutions; used as fat emulsifier, wetting agent, detergent in cosmetics, pharmaceuticals and toothpastes; also as research tool in protein biochemistry. Sodium Lauryl Sulfate,Irium,Dodecyl Sulfate, Sodium,Lauryl Sulfate, Sodium,Sulfate, Sodium Dodecyl,Sulfate, Sodium Lauryl
D013816 Thermodynamics A rigorously mathematical analysis of energy relationships (heat, work, temperature, and equilibrium). It describes systems whose states are determined by thermal parameters, such as temperature, in addition to mechanical and electromagnetic parameters. (From Hawley's Condensed Chemical Dictionary, 12th ed) Thermodynamic
D015394 Molecular Structure The location of the atoms, groups or ions relative to one another in a molecule, as well as the number, type and location of covalent bonds. Structure, Molecular,Molecular Structures,Structures, Molecular
D050337 Trimethyl Ammonium Compounds QUATERNARY AMMONIUM COMPOUNDS containing three methyl groups, having the general formula of (CH3)3N+R. Ammonium Compounds, Trimethyl
D052578 Ionic Liquids Salts that melt below 100 C. Their low VOLATILIZATION can be an advantage over volatile organic solvents. Ionic Liquid,Ionic Solvents,Liquid, Ionic,Liquids, Ionic,Solvents, Ionic
D055664 Electrochemical Techniques The utilization of an electrical current to measure, analyze, or alter chemicals or chemical reactions in solution, cells, or tissues. Electrochemical Technics,Electrochemical Technic,Electrochemical Technique,Technic, Electrochemical,Technics, Electrochemical,Technique, Electrochemical,Techniques, Electrochemical
D058767 Protein Unfolding Conformational transitions of the shape of a protein to various unfolded states. Unfolding, Protein

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